Quick Tip: Exposure Compensation

In every photo you take, your camera’s metering system will do its best to give you an estimate of what settings (Shutter speed, aperture, and ISO if your camera supports Auto ISO) would properly expose the scene. Unfortunately, your built-in camera meter isn’t perfect. In scenes where luminance is unusual, such as when taking photos in the snow or with a subject being strongly backlit, the camera’s metering system is misled.

Thankfully most camera bodies come with a function called exposure compensation to correct the metering system. Measured in units of exposure value (EV), one can either go for less exposure (negative values) or more exposure (positive values). The general rule is that if a scene is darker than average with a subject in a more lit area, then you need to go for a negative compensation to avoid over-exposure. Conversely, if a scene is lighter than your average scene and you wish to still get detail out of your darker areas, then you need to for a positive compensation to over under-exposure.

If you are confused, think about it in terms of a sunset landscape photo and a shadow filled portrait. In the sunset photo, we may want to capture the beautiful sky but also some of the land to give a sense place. Because the sky is extremely bright and the land is very dark, our camera might think there is plenty of light to expose both the sunset and our landscape properly. This may not be the case, and our image may be under-exposed. A positive exposure compensation would aid to properly expose the entire image. Say we have a portrait of a person with a spotlight on them, but the rest of the photo is dark shadows. The camera’s immediate response is: “This scene is very dark - I’d better recommend increasing exposure!” This leads to a scene that is over-exposed. In this situation, a negative exposure compensation will prevent the camera from blowing out the details of the person of focus.

Using techniques like spot metering (instead of scene averaging metering systems) can aid in acheiving the exposure you’re looking for. Some cameras support auto exposure bracketing (AEB) which make this process painless. Exposure compensation requires an understanding of light in a situation. Nothing will teach you how to use exposure compensation better than loads of practice.

Is there any reason to use exposure compensation when shooting in manual mode? I have always found myself setting the aperture and shutter speed to give me an exposure I like for the scene I am shooting. This way I always know the exposure will always be right even I change subjects or recompose my shot. In your example with shooting a person against a bright sky, if you include more or less of the sky from one shot to the next, you will need to modify the exposure compensation. However if you were to just set your exposure by spot metering the person, you can recompose all you like and not have to worry about whether the person will be correctly exposed or not.

Noah: EV is there to give you more control when you’re using the automatic modes because the system will always try and meter for the standard exposure. On most cameras, exposure compensation isn’t used when you’re in manual because the meter isn’t driving the rest of the settings. If you dial in an exposure that meters at -2/3, then there’s you have it; you have manually created what an automatic mode would have with a -2/3 EV.